Well, it depends on what you want. The half faired Sprint RS looses the single sided swing arm from the T5 / ST and instead uses a new double sided swingarm similar to what is found on the TT600. Because of this, it won't utilize the ST hard bag set up although it has soft luggage available. The ST is the tourer while the RS is much more of a sport model.
While on the subject, take a read through this posted to a list on the differences betweenn Triumph Models.
From: Timothy Tokarsky <tokarsky@third-wave.com>
Subject: RS's, ST's, S3, Daytona
Here's my .02 on the RS, ST, S3, Daytona question. I'm in a little bit of a unique position because as a dealer, I get a frequent amount of time on all four (why do you think I own the dealership anyway?!). I prefer to ride very fast, very often. Well.. here goes..
The ST is the most refined, technologically perfected motorcycle in Triumph line up. It does the sport touring thing better than any bike in the lineup, and maybe any other lineup. The hard bag addition is excellent. If sport touring is your thing, this is the bike for you. However, it will not be the twisty king, nor will it be the stop and go king.
The Daytona is the uncompromising king of aggressive sport riding for Triumph. Blazing fast down the shutes. And the only bike in Triumph's lineup which will beat it in the twisties is the TT600 (which will, if you keep it singing, arrrgh). The Daytona isn't the funnest bike in the world to own if you are in a lot of stop and go traffic.....
The Speed Triple is! It is very comfortable to ride both slow and fast. It corners well and makes a decent touring bike. It does have a few drawbacks though.. The Speed Triple will not outhandle the TT, Daytona, or RS. It does not have the front end weight bias that the other have and, combined with the oversquare rear tire is more adept to a cornering style that "backs" the bike into a corner rather than just hotly driving it in. Believe me, much as a love my S3 (I own a 98) anyone can ride a Daytona, TT, or RS much faster thru the corners than an S3 will allow you to. That's a fact, subject of course to those who put 180's, a narrow rim, and clip on's on their s3. I've proved it to myself and others countless times. The other "issues" with the S3 are it's a little harder on both tires if aggressively ridden, and it and the Daytona are more time consuming to do valve adjustments on (because of the frame geometry).
The Sprint RS is very close to the Daytona and TT in handling, excepting a little front end dive if heavy breaking at the corner entrance. It can be ridden very, very aggressively into and thru the corners. You can run into a corner nearly as fast as a TT, which I attribute to both it's smaller, more rounded rear rim and tire combination and it's front end geometry which really helps it's quick flickability. A Daytona will crush it and every other model Triumph driving off a corner. Lose a tooth on the RS's front countershaft sprocket and it will run with a Speed Triple down the shutes!
The RS is the bang for the buck winner. Put a set of ST bars on it and it is a great, ST like sport tourer. Add a front sprocket and it will give an S3 fits in a drag race. It's easy to service, easy on tires, and there are some real deals out there on them. IMHO!
Thanks, TIM